全文获取类型
收费全文 | 53666篇 |
免费 | 5039篇 |
国内免费 | 2741篇 |
专业分类
电工技术 | 2895篇 |
技术理论 | 3篇 |
综合类 | 4438篇 |
化学工业 | 10520篇 |
金属工艺 | 1680篇 |
机械仪表 | 2789篇 |
建筑科学 | 5044篇 |
矿业工程 | 1767篇 |
能源动力 | 1600篇 |
轻工业 | 6864篇 |
水利工程 | 2442篇 |
石油天然气 | 2957篇 |
武器工业 | 424篇 |
无线电 | 4136篇 |
一般工业技术 | 4630篇 |
冶金工业 | 2417篇 |
原子能技术 | 1033篇 |
自动化技术 | 5807篇 |
出版年
2024年 | 82篇 |
2023年 | 647篇 |
2022年 | 1058篇 |
2021年 | 1480篇 |
2020年 | 1601篇 |
2019年 | 1608篇 |
2018年 | 1460篇 |
2017年 | 1658篇 |
2016年 | 1908篇 |
2015年 | 1879篇 |
2014年 | 3222篇 |
2013年 | 3242篇 |
2012年 | 3922篇 |
2011年 | 3944篇 |
2010年 | 3018篇 |
2009年 | 3386篇 |
2008年 | 2936篇 |
2007年 | 3708篇 |
2006年 | 3348篇 |
2005年 | 2927篇 |
2004年 | 2437篇 |
2003年 | 2192篇 |
2002年 | 1854篇 |
2001年 | 1504篇 |
2000年 | 1202篇 |
1999年 | 995篇 |
1998年 | 736篇 |
1997年 | 628篇 |
1996年 | 472篇 |
1995年 | 481篇 |
1994年 | 359篇 |
1993年 | 293篇 |
1992年 | 253篇 |
1991年 | 167篇 |
1990年 | 123篇 |
1989年 | 115篇 |
1988年 | 98篇 |
1987年 | 53篇 |
1986年 | 50篇 |
1985年 | 64篇 |
1984年 | 55篇 |
1983年 | 37篇 |
1982年 | 32篇 |
1981年 | 27篇 |
1980年 | 28篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1976年 | 11篇 |
1964年 | 21篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Vincent Cantarel David Lambertin Arnaud Poulesquen Fabrice Leroux Guillaume Renaudin Fabien Frizon 《Ceramics International》2018,44(9):10558-10568
This work investigates emulsion templating to synthesize hexadecane oil/geopolymer composites. In a system with hexadecane as the internal (dispersed) phase and an alkali activated continuous phase without added surfactant, adding aluminosilicate clay particles does not increase resistance against creaming or coalescence, while adding a surfactant (L35 or CTAB) stabilizes the solid-liquid interface. Infrared studies and rheological studies of the associated geopolymerization determined that the presence of the organic phase or surfactant has no significant effect on the geopolymerization kinetics, as determined by the change in time of the Si-O-T IR stretching frequency and the rheological moduli involved during the process. The stabilization of the organic template is reminiscent of Pickering emulsion even though we employ a much greater amount of inorganic material for geopolymer formation. Although the addition of surfactant has a significant effect on the behavior of the paste, the percolation of the network remains unmodified, highlighting the fact that the phenomenon is not dependent on viscosity. Finally, rheological measurements were used to obtain the mass fractal dimension of the as-made gel network, which is able to differentiate the interfacial effect between surfactant molecules with a slightly denser interphase when a cationic surfactant is used. 相似文献
72.
The technology to produce compatibilized blends of liquid crystalline polymer and highly amorphous cyclic olefin copolymers through two novel approaches were studied. The first approach was to use silane-functionalized halloysite nanotube as nonspecific compatibilizer and the second method was reactive compatibilization. The study of blends and their resulting microstructure; their thermal, mechanical, and viscoelastic properties were investigated. The kinetic study of blends compatibilized through both routes was performed. 相似文献
73.
In this article, a theoretical model for predicting the equilibrium morphology of gas–liquid Janus droplets was built. Based on this model, the effects of bubble radius and volume ratio on morphology change was systematically studied. The increase of bubble radius causes the two parts (bubble and oil drop) in Janus droplets tend to merge while the impact of volume ratio is complicated. When volume ratio increases, these two parts firstly tend to merge, then gradually separate. The accuracy of this model was verified by experimental results. 相似文献
74.
四川省兆迪水泥有限责任公司2500t/d新型干法熟料生产线,于2014年7月11日重建点火投产。生产过程中针对工厂高镁石灰石的原料特点,注意总结工艺操作、熟料质量等方面的经验,采取了积极有效的措施,取得了较好的效果。 相似文献
75.
This article deals with the evaluation of pressure drop and consumption of energy for a steady-state solvent extraction in a horizontal pulsed sieve-plate column, which are important for the design and optimization of the periodic-flow processes for industrial applications. In this study, the pressure drop and the position of loading points are investigated. Moreover, a mathematical evaluation on the energy consumption in the case of a pulsed flow is conducted, and besides the influence of pulsation intensity, the effect of geometrical parameters including the plate spacing and plate-free area is investigated as well. The results of this study are helpful for optimization of column geometry targeted to higher performance and lower energy consumption. 相似文献
76.
CFD Modeling of Active Volume Creation in a Non‐Newtonian Fluid Agitated by Submerged Recirculating Jets 下载免费PDF全文
Computational fluid dynamics (CFD) models were employed to investigate flow conditions inside a model reactor in which yield stress non‐Newtonian liquid is mobilized using submerged recirculating jets. The simulation results agree well with the experimental results of active volume in the reactor obtained using flow visualization by the authors in a previous study. The models developed are capable of predicting a critical jet velocity (vc) that determines the extent of active volume obtained due to jet mixing. The vc values are influenced both by the rheological properties of the liquid and the nozzle orientation. The liquid with higher effective viscosity leads to higher vc for a downward facing injection nozzle. However, an upward facing injection nozzle along with a downward facing suction nozzle generates enhanced complementary flow fields which overcome the rheological constraints of the liquid and lead to lower vc. 相似文献
77.
为降低烟草中噁霉灵检测中的基质干扰,提高检测灵敏度和和稳定性,通过试验建立了以QuEChERS为样品前处理方法、液相色谱串联质谱仪为检测仪器的烟草中噁霉灵残留检测方法。样品加水浸润后,经丙酮提取、盐析试剂包除水、石墨化炭黑除杂后,采用Agilent ZORBAX 300SB-C8液相色谱柱(2.1 mm×100 mm,1.8 μm)分离,甲醇-水程序洗脱,ESI雾化,串联质谱MRM检测。结果发现,该方法在0.0025~0.0500 mg/L范围内线性良好,决定系数r2=0.9996,定量检测限1.06 μg/L,回收率在90.8%~92.0%之间,相对标准偏差为5.1%。运用该方法测定烟草中的噁霉灵,操作简单,检测精度高,满足CORESTA对烟草农残检测的要求。 相似文献
78.
研究离子液体作为添加剂对石墨烯润滑油分散和润滑性能的影响。通过改变离子液体质量分数、超声功率以及时间等条件,考察离子液体/石墨烯润滑油的分散稳定性;采用Rtec多功能摩擦磨损试验机,以Si3N4/钢为摩擦副,考察不同条件下离子液体/石墨烯润滑油的摩擦学行为;采用扫描电镜和超景深显微镜对磨损表面进行分析,探究离子液体作为添加剂的润滑机制。结果表明:离子液体质量分数为0.002 5%、超声时间为60 min,超声功率为600 W时石墨烯润滑油的分散性和稳定性均显著提高;加入离子液体后,石墨烯润滑油的润滑性能提高,其摩擦因数随离子液体质量分数的增加而下降,随超声功率的增加而降低,随超声时间的增加而增加。研究发现,由于离子液体阳离子的长链结构和自身黏度较大,离子液体构成的润滑膜较厚且易于吸附在摩擦副表面,并与石墨烯发生协同作用形成了混合润滑膜,从而避免了摩擦副之间的直接接触,改善了摩擦磨损性能。 相似文献
79.
80.
Hua Zhao Michael S Franklin 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(9):2301-2310
Coal is the most abundant fossil fuel. Direct combustion of low- and medium-rank coals causes alarming environmental impacts. Therefore, it is crucial for coal to undergo pretreatments before its efficient utilization [such as coal to liquid (CTL) processes]. Conventional pretreatment methods suffer from several limitations including the use of volatile organic solvents, environmental hazards, strong reaction conditions (e.g. high temperature and pressure), consumption of large quantities of nonrecoverable chemicals (e.g. bases used in aqueous alkaline digestion), or being only effective for specific coals. On the other hand, coal pretreatment by nonvolatile ionic liquids (ILs) could lead to partial coal dissolution/swelling and structure disruption, which is a critical step before coal liquefaction, hydrogenation, pyrolysis or the inhibition of oxidation/combustion. In addition, ILs are suitable solvents for extracting sulfur compounds from coal, asphaltenes from Direct Coal Liquefaction Residues (DCLR) and phenolic compounds from coal tar. This review will discuss these aspects of coal pretreatments by ILs, and identify how ILs could lead to a cleaner and more efficient utilization of coal resources. © 2020 Society of Chemical Industry 相似文献